Question

Why do human beings have difficulty breathing at high elevations?

• A. $O_2$ makes up lower percentage of air there
• B. The temperature is lower there
• C. The barometric pressure is higher there
• D. $P{O}_2$ is lower there

Answer 1

The correct option is A $O_2$ makes up lower percentage of air there

Human beings have difficulty breathing at higher elevations because the air at higher altitudes is colder, less dense and fewer oxygen molecules. At higher altitudes, air pressure is low which makes molecules farther apart because of which oxygen makes up a lower percentage of air there. At high altitudes, the lower air pressure makes it more difficult for oxygen to enter our vascular systems. The higher the elevation, the more difficult breathing becomes. Acute mountain sickness is caused by reduced air pressure and lowers oxygen levels at high altitudes.

So, the correct answer is 'option A'.